Arylidene and azomethine compounds are used as dyes for fibers, or are used in paints or silver halide photographic materials.
A dye is added to a silver halide emulsion layer or a non-light-sensitive hydrophilic colloidal layer of the silver halide photographic material to absorb light of a specific wavelength. The dye contained in the silver halide photographic material must satisfy the following conditions (1) to (5).
(1) Appropriate Spectral Absorption
The absorption wavelength region is determined according to use of the dye.
(2) Photographically Chemical Inactivity
The dye should not chemically affect the performance of the photographic material (particularly, of the silver halide emulsion layer). In more detail, the dye must not impair the sensitivity, must not fade the latent image, and must not cause fogging.
(3) Easy Bleach or Removal
The dye functions in principle during imagewise exposure. After exposure, the dye must be bleached or removed from the photographic material. If the dye remains in an obtained image, the image would be colored with the dye. Therefore, the dye should easily be bleached or removed by processing solutions (such as a developing solution, a bleaching solution).
(4) Fast to Diffusion
The dye functions in a specific layer of the photographic material. The dye should not be diffused into other layers. For example, an antihalation dye (should be contained in a non-light-sensitive colloidal layer) diffused in the emulsion layer would degrade the sensitivity of the emulsion layer.
(5) Stability
The color of the dye must not change or fade while the photographic material or a solution of the dye is stored.
It is generally difficult to satisfy the conditions (3) and (4). The dyes satisfying the condition (3), which are easily bleached or removed are also easily diffused into other layers. On the other hand, the dyes satisfying the condition (4), which is hardly diffused are difficult to be bleached or removed.
A silver halide photographic material comprising a dye satisfying the conditions (3) and (4) was proposed. The material contains solid fine particles of the dye having a weak acidic group (e.g., carboxyl). Since the weak acidic group does not dissociate in coating solutions (which are generally acidic or neutral) for preparing the layers of the material, the dye is insoluble in the solutions. Hence, the dye can be incorporated in the form of solid fine particles, which hardly diffuse into other layers. The weak acidic group dissociates in processing solutions (which are generally alkaline), and hence the dye is soluble in the solutions. Accordingly, the dye can be easily removed from the photographic material with the processing solutions.
Japanese Patent Provisional Publications Nos. 3(1991)-7931, 4(1992)-37841, 4(1992)-37842 and 4(1992)-45436 disclose silver halide photographic materials comprising arylidene or azomethine dyes in the form of solid fine particles.